Inhibition of Colony Stimulating Factor 1 Receptor Suppresses Neuroinflammation and Neonatal Hypoxic-Ischemic Brain Injury.

Bohao Zhang,Yunwei Ran,Shusheng Zhang,Huachen Huang,Fang Zhang,Siting Wu,Xiaoan Zhang,Changlian Zhu

doi:10.3389/fneur.2021.607370

Abstract

Hypoxic-ischemic (HI) brain injury is a major cause of neonatal death or lifetime disability without widely accepted effective pharmacological treatments. It has been shown that the survival of microglia requires colony-stimulating factor 1 receptor (CSF1R) signaling and microglia participate in neonatal HI brain injury. We therefore hypothesize that microglia depletion during a HI insult period could reduce immature brain injury. In this study, CD1 mouse pups were treated with a CSF1R inhibitor (PLX3397, 25 mg/kg/daily) or a vehicle from postnatal day 4 to day 11 (P4–11), and over 90% of total brain microglia were deleted at P9. Unilateral hemisphere HI injury was induced at P9 by permanently ligating the left common carotid arteries and exposing the pups to 10% oxygen for 30 min to produce moderate left hemisphere injury. We found that the PLX3397 treatment reduced HI brain injury by 46.4%, as evaluated by the percentage of brain infarction at 48 h after HI. Furthermore, CSF1R inhibition suppressed the infiltration of neutrophils (69.7% reduction, p = 0.038), macrophages (77.4% reduction, p = 0.009), and T cells (72.9% reduction, p = 0.008) to the brain, the production of cytokines and chemokines (such as CCL12, CCL6, CCL21, CCL22, CCL19, IL7, CD14, and WISP-1), and reduced neuronal apoptosis as indicated by active caspase-3 labeled cells at 48 h after HI (615.20 ± 156.84/mm2 vs. 1,205.00 ± 99.15/mm2, p = 0.013). Our results suggest that CSF1R inhibition suppresses neuroinflammation and neonatal brain injury after acute cerebral hypoxia-ischemia in neonatal mice.

Highlights

Perinatal hypoxic-ischemic (HI) brain injury is a clinical syndrome associated with oxygen deprivation and is a major cause of neonatal death and long-term neurofunctional disabilities with limited therapies available [1,2,3,4,5,6,7]
Neonatal mice were treated with PLX3397 (25 mg/kg body weight) or vehicle at postnatal day 4 (P4) prior to HI induction (Figure 1A)
We found that brain microglia expressed colony-stimulating factor 1 receptor (CSF1R) in neonatal mice (Figure 1B), and oral administration of PLX3397 for five consecutive days can effectively reduce ∼90% of microglia in the brain of normal neonatal mice (Figure 1C)

Summary

Introduction

Perinatal hypoxic-ischemic (HI) brain injury is a clinical syndrome associated with oxygen deprivation and is a major cause of neonatal death and long-term neurofunctional disabilities with limited therapies available [1,2,3,4,5,6,7]. CSF1R in Neonatal Hypoxic-Ischemic Injury occurs as early as minutes after the insult and is a key contributor to acute perinatal HI brain injury [8,9,10,11]. After cerebral HI, brain microglia change their phenotype, promote the production of inflammatory factors, and recruit peripheral immune cells [12,13,14]. The activated microglia change to the anti-inflammatory state and promote angiogenesis, tissue remodeling, and neurorepair at later stages after HI brain injury [14]. The role of microglia in perinatal HI brain injury remains poorly understood [14]

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Results

Conclusion